Development and experimental study on visualization test platform for water inrush evolution process of coal seam mining floor

Physical simulation test can directly show the whole process of mining floor water inrush,obtain diversified information of mining floor water inrush disaster,and has become an effective scientific research means to study the mining of confined water.In this paper,four modules of water inrush flow monitoring,flexible overburden loading,horizontal graded loading and constant pressure steady flow test module are modified which realizes regional quantitative monitoring of water inrush,flexible uniform stress distribution of similar materials in overburden,independent loading on both sides and sealing in all directions.Taking a coal mine in Shandong threatened by floor confined water as the engineering background,with the help of the up graded test system andnon hydrophilic similar simulation materials,the formation of water inrush channel,the evolution of flow disaster and the change of aquifuge stress are studied.The test results show that:according to the expansion characteristics of the floor visible fractures,the floor water inrush is divided into horizontal and vertical evolution stages,horizontal periodic evolution stages and catastrophic water inrush stages;In the first stage,the main seepage area of the confined water top interface first occurs under the open off cut,and the position does not change with the coal mining.With the expansion of the visible fractures to the confined water aquifer and the advancing direction,the scope of the main seepage area becomes larger and the flow rate increases significantly.In the second stage,with the formation of new fractures under the moving coal wall,the fractures produced by the previous mining cycle are closed,the fracture expansion presents periodic change characteristics,and the main seepage area flow presents a periodic change trend of decreasing,increasing,decreasing and increasing.In the second stage,after the formation of water inrush channel,the main seepage area becomes the source of confined water inrush,the flow rate of other areas is increased,and no mutation occurred in other areas.The sudden change of flow rate at the beginning of this stage can be used as early warning information of water inrush.The test results not only provide experimental guidance for the evolution of floor water inrush and the characteristics of water inrush flow in the process of mining above confined water in the middle and eastern mining areas,but also provide reference for mine safety evaluation,disaster prediction and prevention.